Garmin Personal Navigator GPS 45XL Owner's Manual & Reference

Contents

DGPS Interface (continued)The RTCM/NMEA selection controls the GARMIN GBR-21 differential beacon receiver. Once a RTCM setting hasbeen selected, the GPS 45XL will either automatically try totune the last frequency and bit rate you selected or willswitch to the default frequency of 304.0 kHz with a bit rateof 100 bps if no previous beacon has been tuned. You mayalso enter your own frequency and bit rate if desired.To enter a DGPS beacon frequency:1. Highlight the ‘freq’ field and press E.2. Enter the desired frequency and press E.3. Highlight the ‘rate’ field and press E.4. Use U and D to select the desired transmission rate.5. Press the E key to confirm your entry.When the GPS 45XL is receiving DGPS correctionsfrom the GBR-21, the ‘beacon receiver’ section of the I/Osetup page will display the beacon frequency and signalstrength, as well as the distance from the transmitter to thebeacon receiver. At the bottom of the beacon receiver field,a status message will keep you informed of DGPS activity:• A ‘tuning’ message will be displayed while a beaconsignal is being tuned.• Once the beacon signal has been tuned, a ‘receiving’message will be displayed.• If a beacon signal is tuned and no corrections arebeing received, a ‘no data’ message will be displayed.• If a beacon signal cannot be tuned, a ‘no status’ mes-sage will be displayed.The GPS 45XL will also display one of three alert mes-sages concerning DGPS operation through the messagepage:No DGPS Position— not enough data is available tocompute a DGPS position.No RTCM Input— the beacon receiver is not properlyconnected or the baud rates do not match.RTCM Input Failed— DGPS data was being receivedbut has been lost.52ReferenceInterface SetupDGPSInterfaceOnce a RTCM option isselected, you must manuallytune the beacon receiverfrom the frequency field.The message page will alertyou to any problems relat-ing to DGPS operation. Youmay also monitor the DGPSstatus from the status fieldon the interface setup page.